Carpal tunnel syndrome (CTS), is the most common peripheral neuropathy, but currently there are no biomarkers to help guide treatment or to predict patient specific outcomes. We hypothesize that ultrasound detectable variations in nerve, tendon and subsynovial connective tissue (SSCT) mobility in patients with CTS may be useful clinically as functional biomarkers that correlate with, and thereby serve as predictors for treatment response. To test this hypothesis, we propose a clinical study in which patients presenting for treatment of CTS will be monitored by ultrasound and by clinical assessment before and after surgical and non-surgical treatment. We will correlate the clinical outcomes with the initial ultrasound motion patterns that we have found to be most variable in CTS patients. We will also test the hypothesis that successful treatment results in a change towards normal in the affected ultrasound variables. There are 4 Specific Aims. Aim 1 is to assess the ability of the functional biomarkers we have identified (the ratio of SSCT to tendon motion, dorsal nerve motion, and changes in nerve shape with motion) to predict outcome after steroid injection in patients with CTS. Aim 2 is to assess the ability of the functional biomarkers we have identified to predict outcome after surgery in patients with CTS. Aim 3 is to test our secondary hypothesis that treatment response after both injection and surgery correlates with a change towards normal in the affected ultrasound variables. Aim 4 is to, using the results from Aims 1-3, identify additional biomarkers that may correlate with treatment outcome, and to identify any composite clinical and biomarker measures that may improve the ability to predict outcome after treatment for CTS. If these aims are achieved, functional biomarkers will, for the first time, be available t tailor treatment for specific patients with CTS. This new US tool can be rapidly translated into clinical use, since the equipment is commonly available and the new algorithms could be rapidly disseminated.